On the deformation mechanism of olivine single crystals at lithospheric temperatures: an electron tomography study

Alexandre Mussi (1) , Maula Nafi (1) , Sylvie Demouchy (2) , Patrick Cordier (1)

1 UMET - Unité Matériaux et Transformations - UMR 8207
2 Géosciences Montpellier

We present an electron tomography study of dislocations in deformed olivine single crystals, at ca. 0.5 T m, along two distinct orientations. The easiest slip systems are [001](100) and [001]{110}. Disorientating a single crystal away from easy glide conditions leads to massive cross-slip, which generates three-dimensional dislocations, and thus contributes to hardening. Fast motion of curved non-screw dislocation in those planes leaves long straight screw dislocations which bear lattice friction and control plastic strain. We have identified several hardening mechanisms. Non-screw [001] dislocations interact elastically to form dipoles. Recovery mechanisms leading to dipole annihilation are observed, but they are slow at those temperatures and produce numerous sessile loops. These loops represent obstacles for gliding dislocations. Interactions between dislocations and sessile loops produce sessile segments (super jogs), which efficiently impede dislocation motions.

Mots clés: olivine; dislocation; cross-slip; rheology; plasticity; electron tomography; hardening

Domaines: Sciences de la Terre; Science des matériaux [cond-mat.mtrl-sci]

Alexandre Mussi, Maula Nafi, Sylvie Demouchy, Patrick Cordier. On the deformation mechanism of olivine single crystals at lithospheric temperatures: an electron tomography study. European Journal of Mineralogy, 2015, European Journal of Mineralogy, 27 (6), pp.707-715. ⟨10.1127/ejm/2015/0027-2481⟩. ⟨hal-01277821⟩